In an electronic component mounting apparatus, an electronic component provided on parts feeder is picked up by sucking with a nozzle of transfer head to be mounted on a circuit board.
The size of electronic components supplied on parts feeder widely varies from quite large to tiny depending on type of component. Therefore, the nozzle has to be replaced from time to time with other nozzle that fits to a specific component type. For the nozzle exchange, a transfer head goes to a place above a nozzle stocker and makes up and down action.
FIG. 7 is a chart used for explaining a procedure of the nozzle exchange in a prior art electronic components mounting apparatus. Underneath a transfer head 1 is a nozzle holder 2 for holding a nozzle 3a. A nozzle stocker 4 is provided with several number of holes 5(six holes in the present exemplary apparatus) arranged in a straight line row stretching lengthwise; in the respective holes nozzles 3b-3f are kept. The nozzles are put on use sequentially in the order 3a, 3b, 3c, 3d, 3e and 3f. In FIG. 7, the transfer head 1 is holding a nozzle 3a, which was kept in the leftmost hole 5 of nozzle stocker 4; therefore the leftmost hole 5 is vacant.
For replacing the nozzle 3a now on transfer head 1 with a nozzle 3b which is kept in the rightmost hole 5, the transfer head 1 goes above the leftmost vacant hole 5 and makes an up and down action to return the nozzle 3a to the hole 5(see nozzle 3a illustrated with broken lines), and then goes to a place above the nozzle 3b(stroke L1) and makes another up and down action there to attach the nozzle 3b on nozzle holder 2. After the nozzle exchange is thus finished, the transfer head 1 begins a next operation of mounting electronic components using the nozzle 3b. 
For replacing the nozzle 3b with a nozzle 3c, the transfer head 1 goes to a place above the rightmost hole 5 to return the nozzle 3b to the hole 5 in a same manner as described above, and then goes above the nozzle 3c(stroke L2) to attach the nozzle 3c on nozzle holder 2. Exchange to a nozzle 3d, to a nozzle 3e and to a nozzle 3f are conducted in a same manner as described above.
However, in the conventional method where the nozzles 3a-3f are kept in the holes 5 without assuming any specific order, the strokes L1, L2, L3, . . . of transfer head 1 required for nozzle exchange are considerably long, and the tact time for nozzle exchange becomes long to the deterioration in efficiency of components mounting work. In some practical cases, the nozzle has to be replaced for more than 10 times per one circuit board. Reducing the tact time required for nozzle exchange is therefore a key factor in improving the mounting efficiency.
The present invention aims to present a method of mounting electronic components with a significantly reduced tact time, as well as an apparatus for mounting electronic components by the same method.